Modulation of light localization in the iridophores of the deep-sea highlight hatchetfish Sternoptyx pseudobscura under magnetic field

Efficient light control by certain tissue in bioluminescent fish offers potential for new optical devices. In the world’s deep-seas, there are numerous fish species with such bioluminescence yet to be discovered. One such species, the deep-sea highlight hatchetfish Sternoptyx pseudobscura, which was found at depths of ca. 800–900 m in the neighboring waters off the Amami Islands, Japan, exhibits a new form of light-reflection produced in guanine crystal platelets present in the skin Strongly reflecting platelets in the dorsal and anterior-ventral region enhance its reflection in the presence of magnetic fields either in parallel or perpendicular to the incident light. A diamagnetic ordering of the platelet alignment is suggested in producing a small angular rotation of the platelets when placed in a magnetic field. The synchronized ordering of these platelets in parallel possibly modulates the localization of light in a multilayer structure inside the iridophore. The developed method should be useful for investigating the bio-ethological meaning of guanine crystal platelet arrangements in the deep sea fish reflecting light.